A signal having a high frequency (from RF to THz) enables a wide variety of applications, ranging from gigabits/terabits bandwidth communication systems, to molecular analysis, and medical or industrial imaging.
Known semiconductor devices enabling the generation of such signals having a high frequency include a Gunn diode, tunnelling diodes, transit time diodes, transistor (bipolar, FET)-based oscillators, and multiplier based oscillators relying on device non-linearities such as a Schottky diode.
Nevertheless, an upper limit usually associated to semiconductor devices in terms of frequency generation is in the hundreds of GHz. As a consequence, photonic-based devices such as a gas laser, a quantum cascade laser, or photoconduction-based devices are serves in many applications requiring signals having a high frequency.
However, these photonic devices are bulky, require cryogenic temperature, or are not compatible with the ubiquitous silicon semiconductor technologies.
Very recent investigations have reported the emission of a signal having a high frequency (THz) from exotic semiconductor devices and from highly-Boron doped silicon. The first type of devices using exotic semiconductors rely on the use of the new plasma wave theory, however, the maturity of this technology is still in its infancy and has not be demonstrated in silicon. The second, based on B—Si only works at cryogenic temperature that makes its use impractical for widespread commercial applications.